LXR linux/samples/bpf/xdp_sample_pkts

   1// SPDX-License-Identifier: GPL-2.0
   2#include <linux/ptrace.h>
   3#include <linux/version.h>
   4#include <uapi/linux/bpf.h>
   5#include "bpf_helpers.h"
   6
   7#define SAMPLE_SIZE 64ul
   8#define MAX_CPUS 128
   9
  10struct bpf_map_def SEC("maps") my_map = {
  11        .type = BPF_MAP_TYPE_PERF_EVENT_ARRAY,
  12        .key_size = sizeof(int),
  13        .value_size = sizeof(u32),
  14        .max_entries = MAX_CPUS,
  15};
  16
  17SEC("xdp_sample")
  18int xdp_sample_prog(struct xdp_md *ctx)
  19{
  20        void *data_end = (void *)(long)ctx->data_end;
  21        void *data = (void *)(long)ctx->data;
  22
  23        /* Metadata will be in the perf event before the packet data. */
  24        struct S {
  25                u16 cookie;
  26                u16 pkt_len;
  27        } __packed metadata;
  28
  29        if (data < data_end) {
  30                /* The XDP perf_event_output handler will use the upper 32 bits
  31                 * of the flags argument as a number of bytes to include of the
  32                 * packet payload in the event data. If the size is too big, the
  33                 * call to bpf_perf_event_output will fail and return -EFAULT.
  34                 *
  35                 * See bpf_xdp_event_output in net/core/filter.c.
  36                 *
  37                 * The BPF_F_CURRENT_CPU flag means that the event output fd
  38                 * will be indexed by the CPU number in the event map.
  39                 */
  40                u64 flags = BPF_F_CURRENT_CPU;
  41                u16 sample_size;
  42                int ret;
  43
  44                metadata.cookie = 0xdead;
  45                metadata.pkt_len = (u16)(data_end - data);
  46                sample_size = min(metadata.pkt_len, SAMPLE_SIZE);
  47                flags |= (u64)sample_size << 32;
  48
  49                ret = bpf_perf_event_output(ctx, &my_map, flags,
  50                                            &metadata, sizeof(metadata));
  51                if (ret)
  52                        bpf_printk("perf_event_output failed: %d\n", ret);
  53        }
  54
  55        return XDP_PASS;
  56}
  57
  58char _license[] SEC("license") = "GPL";
  59u32 _version SEC("version") = LINUX_VERSION_CODE;
  60